Knockdown piano and utility string chassis therefor



C. F. STEIN May 2, 1950 KNOCKDOWN PIANO UTILITY STRING GHASSIS THEREFOR Filed March 27, 1945 5 Sheets-Sheet l "mull lln uvmvrox.

CHARLES FREDERICK STEIN ATTORN EYS C. F. STEIN KNOCKDOWN PIANO AND UTILITY STRING CHASSIS THEREFOR Filed March 2'7, 1945 5 Sheets-Sheet 2 INVEN TOR.

CHARLES FREDERICK STEIN BY M M r M ATTORNEYS C. F. STEIN May 2, 1950 KNOCKDOWN PIANO AND UTILITY STRING C HASSIS THEREFOR 5 Sheets-Sheet 3 Filed March 2'7, 1945 FIG;

IN V EN TOR.

J IBd I W? i CHARLES FREDERICK STEIN BY M, M, Y m

ATTORNEYS May. 2, 1950 c. F STEIN 2,505,803

KNOCKDOWN PIANO AND UTILITY STRING CHASSIS THEREFOR Filed March 2'7, 1945 5 Sheets-Sheet 4 lul IMI,

Y D s I INIENTOR. '7 I01 CHARLES FREDERICK STEIN A TTORNE Y.

May 2, 1950 c. F. STEIN KNOCKDOWN PIANO AND UTILITY STRING CHASSIS THEREFOR Filed March 27, 1945 5 Q sSheet-5 FIG. 8

(UNITARY CHASIS) CHARLES FR? BY Ila.

, strings in a known manner.

Patented May 2, 19 50 KNOCKDOWN PIANO AND UTILITY STRING CHASSIS THEREFOR Charles Frederick Stein, Ivoryton, Conn., assignor to Pratt, Read & 00., Inc., Ivoryton, Conn., a

corporation of Connecticut Application March 27, 1945, Serial No. 585,053

3 Claims.

This invention relates to knock-down pianos and to unitary string chassis therefor and, while it is of general application, it is particularly adapted for embodiment in relatively low cost pianos which can be fabricated on an assembly production basis while attaining uniform tonal and performance characteristics.

Heretofore, it has been customary to manufactu're pianos largely on an individual custom basis. This has been due primarily to the nature of commercial piano construction and to the difficulty in procuring, in such construction, the desired uniformity of tonal quality and performance. In general the prior commercial piano constructions have comprised a harp or frame, usually of cast iron, on which the strings are stretched. It has been found that if such a harp or frame is made sufficiently rigid and massive to be entirely self-supporting so that it does not require supplementary elements or parts to prevent it from buckling and cracking, it becomes intolerably heavy. Therefore, it has been customary to make the harp lighter than necessary for such self-support and to anchor it rigidly to a stiff massive wooden back, thus forming a composite structure considerably lighter than a cast iron structure designed for the same rigidity, and yet together constitutingvery heavy and cumbersome parts for assembling with the remaining structure of a piano.

It has also'been customary to attach the sounding board carrying the string bridges directly and firmly to the rigid back, as by gluing. Finally, it has been customary to support the composite harp and back and sounding board structure by a rugged supporting casing and to support the keys and keybed, the piano action, the pedals and the pedal action from the back and the casing, arranging the moving parts to operate on the The ruggedness of the casing necessary to support the massive frame assembly and the other elements has contributed to the undesirably high overall weight of the piano instrument, an undesirable characteristic commonly recognized.

' It is an object of the invention, therefore, to provide a new and improved knock-down piano which obviates one or more of the above-named disadvantages and limitations of the prior art piano constructions and which is at the same time simple, economical. and-rugged in construction.

. It is another object of the invention to provide anew and improved knock-down piano embodying one or more of the following advantageous characteristics: extreme ruggedness, light weight, and adaptability to manufacture by assembly production methods with a high degree of uniformity of tonal quality and performance.

It is another object of the invention to provide a new and improved unitary string chassis suitable for use in pianos of the type described and one which is completely self-contained and selfsupporting and adapted to support or to be supported by the piano casing structure.

In accordance with the invention, a knockdown type of piano comprises a casing and a unitary string chassis including a rigid self-supporting metal frame member having an integral wide peripheral flange and a web portion, and a sounding board supported from the frame and forming with the frame means for stretching the piano strings. The flange and the piano casing include registering provisions for forming supporting connections between such casing and the chassis frame.

Further, in accordance with the invention, there is provided a unitary string chassis for use in a piano of the type described comprising a rigid self-supporting metal frame member having an integral wide peripheral flange and a web portion, and a sounding board supported from the frame and forming with the frame means for stretching the piano strings. The flange of the frame member of the string chassis includes provisions for forming supporting connections with a piano casing.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings while its scope will be pointed out in the appended claims.

Referring now to the drawings, Fig. 1 is an exploded perspective front view of a unitary string chassis embodying a feature of the invention; Fig. 2 is a back view of the sounding board to be assembled in the chassis of Fig. 1; Fig. 3 is a back view of the harp or frame of the chassis of Fig. 1; Fig. 3A is a fragmentary cross-sectional view along the lines AA of Fig. 3; Figs. 3B and 3C are cross-sectional views along the lines 3-3 and 0-0 of Fig. 3; Figs. 4A and 4B are side and front views, respectively, of the bracing posts embodied in the chassis of Fig. 1; Fig. 4C is a cross-sectional detailed view of a structure for anchoring the posts of Figs. 4A and 43 to frame of the chassis; Fig. 5 is an exploded perspective view showing the assembly of the chassis and the piano casing; Fig. 5A is a cross-sectional detailed view of an anchoring means for the chassis and piano casing; Fig. 6 is a back view of a modified form of harp or frame for embodiment in the chassis of the invention by means of which the stiffening posts may be omitted; Figs. 6A and 6B are cross-sectional views of a complete unitary string chassis embodying the frame of Fig. 6 and taken along lines A-Aand B-B, respectively, of Fig. 6; Fig. 7 is an exploded perspective view showing the assembly of the chassis embodying the frame of Fig. 6 and a piano casing; while Fig. 8 is a cross-sectional view of a low-upright piano action and string chassis assembly and illustrating the increase in keylength for given overall dimensions.

Referring now to Figs. 1, 2, 3 and 3A-3'C, there is illustrated a strin chassis-adapted to be mounted in the piano casing to provide the knock-down type piano of Fig. 5. The piano comprises a unitary string chassis Ill including a rigid self-supporting cast metal frame member 4?] having a wide peripheral flange l-l a'and a planar web portion llb disposed throughout its entire extent approximately centrally of the flange Ha and preferably including the median plane of the member; that is the flange 'I la ex- ,tendsapproximately equally on either side of the entire web portion llb. The 'web portion comprises a series .of bracing struts llc having cutouts therebetween in order to lighten the weight of the frame'member, the struts llc preferably being provided with stiffening ribs lld on the ,front'faces thereof as indicatedin Fig. 1, the back faces being unribbed as indicated in Fig. 3. The struts ll c are disposed to aid the frame in withstanding the enormous stresses of the strings and to provide intermediate supports of the proper contour for banks of fixed stringpins. The stiffening ribs l'ld are positioned so that channels are provided therebetween on the front face of the frame member in which the strings may be positioned in the usual crossed or over-strung construction ('Fig. l) T-he strings are positioned adjacent to the web portion of the frame member; so that the piano action can extend into the k 3 cavity formed by the flange I la and the plane of the strings as will be further explained.

I The frame member l I has a channel-like recess -l;ie along its upper side and at the back thereof, formed by the upper flange lia and a second integral rflange llf parallel with the peripheral flange Ila. A wooden pin block l2 :is tightly fitted in the recess He and secured zthereto 'by screws or bolts (not shown) extending through the web-portion l lb of the frame. A -series or bank of holes l lg is formed in the bottom of the recess l-le,that is in the web l'lb, adapted to register with the string pins (not shown) mounted in the pin block 12 and to allow the pins to zprotrude through the front face' of the web ll'b and yet to be supported by the web llb where they pass therethrough so that the pins will not split or pull out of the wooden pin block. Groups of fixedstring-pins 1 In are'also mounted in certain of the struts l ic, as shown in Fig. 1,130 cooperate with the adjustable string pins in the pin block H in supporting the piano strings mounted thereon.

f The frame member H is preferably constructed of a high tensile-strength, light metal alloy such as an aluminum-copper magnejum alloy com'- mercially available as Duralumin" or an alloy of magnesium, aluminum and manganese and zinc commercially available as Dowmetalf' In any event the :member ll should be'co'nstructed across-sectional configuration.

4 of a material and with a cross-sectional moment of inertia resulting in a rigidity for a given weight substantially higher than that of the composite cast iron frame and wooden back of conventional pianos. Preferably the material of the frame member I l should have a ratio of Youngs modulus to specific "weight greater than 3x10 and preferably of the order of 3375x10 This ratio may be termed the factor of merit and is an index of the rigidity per pound of metal of the chassis member for any given size and any given In other words, a "string chassis of given dimensions made of a metal with a high ratio will have a higher rigidity for any given weight or will be lighter in weight for-any givenrigi'dity than one made of a metal having a lowerratio. A mean value for this ratio for aluminum alloys of the type mentioned is 3.89 x10 while a typical value for magnesium alloys of the type mentioned is 3.57 x10 The framemember=l I may be provided with a plurality of integral ,piano-action supporting brackets l lb which, asindicated -in Figs. 3B and 3C, are adapted to supportithe piano action and -keybed,.a fragment of which is shownat l4.

The unitary stringchassis of the inventionalso includes a sounding-board l Esupported from the frame ll, specifically being fitted "within the peripheral flange llq. at the back of the frame. 'As indicated in- Fig. 1, the sounding board comprises. a web l5a, preferably of plywood, -rigidly supported in a peripheralframe 15b and including the median plane thereof so that the frame lfib'spac'es the web lBas uita-bly from the web llb of the frame member I1 and also from the back face of the frame member l l. The frame-l5b may be rigidlysecured in anysuitable fashion to the web portion Nb of frame H, as by screws (not shown) passing through the web l lb, or through the flange l l f prior to the mounting .of the pinblock l2. Thesoundingboard l5 is also provided with suitable string bridges I50 and-lid secured to the front face thereof and projecting through the cutouts of the frame member II to form with the frame l l .provisions for stretching the piano strings. The sounding board l5 isprovided with a plurality o'fsti'ffening ribs lierigidb' secured to its rear face toiincre'ase itsrigidity and improveits tonal-qualities.

The unitary string chassis also includes a series of posts 16. preferably. of channel cross-section as illustratedextendihg between and bracing the opposed flangel l-b and-flower peripheral flange Illa-of the frame -l l -These posts may besecu-red to the flangesl-lq and -l;l;f -byscrews or bolts passing through the holes l- 6 a registering therewith. The .posts l-6 are proportioned to fit closely over the pin block 42 and toaid in retaining it firmly within the recess El le of the f-ramemember.

In .order to ;aid-'in stiffening the frame -member ll, the posts l'6 are anchored to the web :portion lib thereof at desired intermediate points. To this end there are provided aaplural-ity -of anchor bolts -l'l shownin-detail in-F-igAC. The bolt 11 has a head i'la threaded'into-or otherwise rigidly secured to the web of'apost 16. The shankof the bolt i"! isprovidedwith a shoulder l%lb beyond which projects a threaded portion l 'lc'on which'is disposed a nut Hd for dra-wingiup the web l lb of the frame-=member against thashoulder ll-b, thus-securely anchbring the pestle to the web portion llb of the frame member. It will be understood that the bolts 1 I :pass "through suitable apertures l5 "in the web portion l5b "of the soundingboard.

spouses In Fig. there is shown in perspective the manner in which the unitary string chassis is assembled with a casing. The flanges i In of the frame member I l and the side members Isa of a casing l8 include registering provisions for forming supporting connections between the frame II and the piano casing; for example, for supporting the casing from the frame, in the event that the casing is of the non-supporting type, or for supporting the frame from the piano casing structure including the keybed I4 and piano legs If in the event the casing structure is of the supporting type. Specifically, the side members .180. of the casing have a plurality of Supporting bolts I 82) which may be mounted with their heads lmbedded in the casing member lila as shown in Fig. 5A. The flanges Ha are provided with a plurality of bolt holes or apertures ilk disposed to register with the bolts I81) and the bolts llb are provided with suitable nuts 18a for engaging and securing the flanges i la to the casing members [8a. The piano casing may also include a conventional top member I803, a. front member IBe and the legs 18 As indicated in Fig. 5 the unitary string chassis of the invention, when included in a piano of the upright type, also forms a back for the piano.

In Figs. 6, 6A and 6B and Fig. 7 are illustrated a modified form of the invention in which the posts l6 of the previously described structure are omitted and the bracing struts lie of the frame member H are provided with additional integral stiffeningribs I Im on their back faces so that these struts have cross sections in the nature of I-beams as indicated in Figs. 6A and 6B. The additional rigidity provided by this construction avoids the necessity for the bracing posts It of the previously described construction. In other respects the construction of the piano and of the unitary string chassis of Figs. 6 and '7 is similar to that described above.

In Fig. 8 there is illustrated a piano assembly including a unitary string chassis embodying the invention in a drop-type piano action suitable for low-upright pianos. In this assembly the keybed It and the action mechanism l9, which may be of conventional construction, are supported from brackets 20 attached to the frame member 1 l by bolts ft or equivalent. In this type of piano, the action mechanism i9 is behind the keys Ma rather than above them, as in the highupright piano. Therefore, for a given overall width of piano, the maximum permissible length of key is decreased. As a result, the keys have a. leverage considerably less than that of the keys of high-upright and grand pianos and require a considerably greater operating force for a given intensity hammer blow; that is the action tends to be stiff and unnatural.

By the use of the invention, however, the space within the flanges Ila and in front of the web portion Hb comprises a cavity into which the piano action may extend, which cavity is of a depth equal to nearly one-half the overall width of the frame member ll. This permits the construction of a more shallow piano with the piano action and keybed extending into the frame cavity or, for a piano of given depth, it permits the use of a longer key leverage. Considering specific typical dimensions, it is customary to limit the overall width of a piano to 24 inches to permit maneuvering it through a standard 30 inch doorway. In the piano illustrated the overall width is 23% inches. In the assembly including the unitary string chassis having an overall width of 4% inches and with the piano action l9 extending into the front cavity of the chassis, there is left 14% inches for the keys Ma. With thesameassembly but with th substitution of a conventional composite back and frame also 4 inches in width but with the action [9 entirely in front of the frame, the key length is reduced to 12%; inches; that is, the use of the string chassis of the invention has increased the permissible key lengthiby 2 inches or slightly more than 20 percent. This very substantial increase in the length of the keys is sufficient to convert an action which would be unacceptably stiff and unnatural to an acceptable one. p

In Fig. 8 also is illustrated the manner of mounting string pins 22 in the pin-block I2, the shanks of the pins 22 bein provided with Wooden bushings where they pass through the apertures Hg, thus being supported by the web l lb. This support of the pins 22 by the web lib minimizes splitting of the pin-block l2 and pulling out of the pins 22.

Thus it is seen that the piano construction and the unitary strin chassis construction of the invention described have a number of distinct advanta es not found in the prior art pianos. Among these may be mentioned that the unitary string chassis is essentially a rectangular frame of I-beam section and is extremely rigid and rugged, avoiding warping. In this construction, also, the strain of the strings is exerted substantially in the plane of the web lib, that is in the median plane of the chassis, avoiding any substantial torsional stresses on any part of the string chassis. This construction further avoids separaton of cast iron frame and wooden back frequently encountered in the conventional prior art composite structure. Further, the unitary string chassis is considerably lighter than such prior composite structure. As a result of the reduction in weight, the unitary string chassis may be readily moved about in the initial preassembly of the unit itself, in any preassembly of the piano in the factory, in shipping, and in the final assembly in a home or showroom. In any assembly operation, the wide flanges of the frame provide adequate bearing and supporting surfaces for connection to the piano casing, while the fastening bolts are readily accessible in front of the strings and back of the sounding board so that the chassis and the casing can be readily disassembled without interference with the strings. Furthermore, the overall cross-section of the frame member Ila, which must resist the tremendous aggregate tension of the piano strings, has a balanced moment of inertia, thereby procuring the maximum rigidity for any given cross-sectional area.

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

I claim:

1. A piano structure for use in an enclosing case, said piano structure comprising a single integral metal frame including a vertically extending web structure and flanges extending on the front and back sides of said web structure at the bottom and sides of said frame, said bot-' tom flange supporting said piano structure at the floor, said side flanges including provisions for individually supporting parts of a separable piano case, said frame including a top flange on said front side of said web structure which forms amuse with said-bottom and side fla-nges a cavity on *flie frontside of said Web structure, pianOstr-ings, moans for supporting said piano strings on' s'aid sixtame withinsaid cavity, said frame including additional flangeonsaid back sideof said web structure "and spaced downwardly from thetop or said frame, a sounding board positioned on 'said back side'of said web structurein 'the cavity slot-med by's'aid additional flange and said bottom send side flanges, a pair of brackets, means for supp'orting said brackets on said frame on said frontside of said-web structure adjacent said side flanges, a piano action, means carried by said 'trame' and said brackets for supporting said piano motion in operating relation 'With said strings With a portion of said action extending into said #cavity on saidiront side of'said Web structure,

.z rliano keys, and means for supporting said piano keys, said frame having peripheral flanges and w-web'structureintegrally connecting said flanges nnd substanti-aHy in a single plane 'cnt'ra'llyof solid flanges;mea'n's rigidly securing said-sounding -board-to'said webstructure on one side thereof and within the limits of said peripheral flange, "mearisior mounting said pianostrings on-the other side of said web structure in the '--c avity iormed'bysaidweb structure andthe adjacent peripheral flange-and at-a distance "from said web structure less than the width of said adjacent peripheral flange; means formounting said piano action on saidfra'xne with a portion of said action Within said cavity in cooperative relation-with said strings, means for-supporting'said piano keys in "operative "relation with said action including brackets extending-out from said otherside of said Web structure, means for securing said brackets to said frame substantially at the flanges on opposite sides thereof, said en-elos-ing case including a plurality of separable parts, said frame having provisionson the fiange'son the sides thereof f or "removabl-y *positioning'and supporting parts of said case thereon.

piano including --an operating structure and "an enclosing case, said operating structure oomimisin'g asoiinding board, piano-strings, a

piano-actiompiano keys; and a-single-metal frame -:1mvm said sounding board, strings, action and keys "mounted -=theron, said fram'e I being 'rnjade of a' matrial -having-a ratio of-Young's'inodulus to'speci-fic weight greater "than 3.0' l'0 and'ineludirigirltegral peripheralfiangcs and a web --st i.ucture 'connecting said fianges and substan- 'tial'ly' in Qasingle plane centrally of said. flanges, wh re yeavmes grammes on each ';side of s aid wveb structure-Hy said'-fiariges,- neans for supporting said sounding board o'ngsa'id 'frame in said cavity-formed said peripheral flange on one -Side offsaidfwebstructure, means for supporting said- ;pian'o strings, piano action and piano "keys 'onisaid'fra'me on the side ofsaid web s truct ure oppositeto said-one side, with said strings, acti on, and'keys being in'oprating position with re speot toeach other and withsaid stringsand aportion of "said action [extending in said cavity iorxned byfsaid; peripheral flange on said opDQsite side 'ojfsaid web structure, said operating structure including provisions ,mrernovably supporting said Case Qnsaidoperating structure.

CHARLE .ER DER Q S EIN- REFERENCES em iolloxving references are of record in the .fil rq th s pat nt:

l UNITED STATES PATENTS 1,11 ,423. 6 'B y:-v --r e 13, 2. 11 91 CQl --..--.J ,3 -;z52 ,234 Collen Mar. 25, 19 3.0 1;758,"I92 'Pressle'y May 20, 19 3 0 1,731,216 pl k Nov. 11, 1930 239 1605 aver n --a-.----.- N 2102898 Huseby Dec. 21, 1937 23313.50 Stein ,Nov. 2 5, 194 7 "FGREIGN iP-ATENTS Number Country 7 Date 5,859 GreatBrita-in May 12, 1 8 8 5 1.93 3 .G eatBr ta n Ma ,1 1893 177,297 Great: Britain Dec. 24, 1937 

